There was an interesting discussion on the Guardian musicblog last week about the seeming dearth of "political" musicians (http://www.guardian.co.uk/music/musicblog/2008/sep/11/1 ).
As you'd expect, opinions differed sharply on the issue & rather than re-hash all the arguments here, I leave it to the discussion for enlightenment.
One of the acts cited as political was the Irish band That Petrol Emotion. Mention was made of a single they released about 20 years ago, "Big Decision". I hadn't heard that track in years, so I went to YouTube & unearthed this gem: